English: Black-throated Loon, Arctic Loon
Russian: Чернозобая гагара
German: Prachttaucher
French: Pongeon arctique
Mongolian: Хилэнгүеэт гахууна, Хилэномруут ахууна
Japanese: オオハム (O-hamu)

Body length: 63-75cm
Wing span: 100-122 cm

Habitat: Unlike Red-throated, breeds on clear, fish-holding freshwater lakes (or sea-bays without tide), builds nest on small islet near waterline. Often gregarious in winter. 

Identification: Appears somewhat larger than Mallard, though shape slimmer. (A few large individuals same size as smallest Great Northern.) Dagger-shaped bill with slightly curved culmen, slimmer than Great Northern’s; carried horizontally. (or nearby; Red-throated’s more clearly upwards) Forehead often steep, hindcrown smoothly rounded. Thick neck (same-thickness head and neck), and has prominent chest at waterline (Red-throated more flat-chested). In flight, compared with Red-throated, neck slightly thicker and carried straighter (less sagging), as is bill; feet always large and obvious, projecting prominently, making wings set close to centre; slightly slower and shallower wingbeats on average than Red-throated in comparable winds (but dependent on individual size; small birds more like Red-throated, large more like Great Northern).

• Adult summer: Velvety pale grey crown and hindneck, black foreneck and throat, and a pattern of distinct white patches of upperbody.
• Adult winter: In profile, at least half of neck dark, visible in flight too, and border between grey hindneck and white foreneck usually highlighted by swarthy line. Generally no white around eye (but beware juv. Red-throated, with can show reduced white). Swimming bird often shows distinctive, isolated white patch on rearmost flanks. Upperparts plane dark grey. Bill (pale) grey with blackish tip.
• Juvenile: (often retained to midwinter, partly to first spring); As adult winter, except pale feather fringes on upperparts form neat, fine scaly pattern ; upperparts slightly paler and browner; tip of bill less blackish.
• 1st summer: Summer plumage only partial.